7 common errors

Some common errors arise again and again
in statistics.
Here are seven to watch out for:

unclear basepoint for graphs

A TV advert used to proudly proclaim:

"X has 25% more active ingredient"

The screen however showed just the top of four test tubes. The words
may have been true, but it looked a lot more than 25% - a truthful advert?

%increases and changes in %difference

If 300 is 50% bigger than 200, is 200 50% less than 300?
In 1990 product A had 10% of market share and now it has 15%. Is that
a 50% increase or a 5% increase? Of course, the market may be only half
as big now, so there may be less of product A sold.
Lesson - be very careful with your language.